Add multithreading test for SamplingCircularQueue, fix implementation.

src/circular-queue.cc

Index: src/circular-queue.cc
diff --git a/src/circular-queue.cc b/src/circular-queue.cc
index 5f7a33eb3a86d0dc71416617300eec7c945b7715..a7c25323e827842a41e00f4469ca917de72f6c0d 100644
--- a/src/circular-queue.cc
+++ b/src/circular-queue.cc
@@ -52,52 +52,44 @@ SamplingCircularQueue::SamplingCircularQueue(int record_size_in_bytes,
     buffer_[i] = kClear;
   }
   buffer_[buffer_size_] = kEnd;
+
+  // Layout producer and consumer position pointers each on their own
+  // cache lines to avoid cache lines thrashing due to simultaneous
+  // updates of positions by different processor cores.
+  const int positions_size =
+      RoundUp(1, kProcessorCacheLineSize) +
+      RoundUp(sizeof(ProducerPosition), kProcessorCacheLineSize) +
+      RoundUp(sizeof(ConsumerPosition), kProcessorCacheLineSize);
+  positions_ = NewArray<byte>(positions_size);
+
+  producer_pos_ = reinterpret_cast<ProducerPosition*>(
+      RoundUp(positions_, kProcessorCacheLineSize));
+  producer_pos_->enqueue_pos = buffer_;
+
+  consumer_pos_ = reinterpret_cast<ConsumerPosition*>(
+      reinterpret_cast<byte*>(producer_pos_) + kProcessorCacheLineSize);
+  ASSERT(reinterpret_cast<byte*>(consumer_pos_ + 1) <=
+         positions_ + positions_size);
+  consumer_pos_->dequeue_chunk_pos = buffer_;
+  consumer_pos_->dequeue_chunk_poll_pos = buffer_ + producer_consumer_distance_;
+  consumer_pos_->dequeue_pos = NULL;
 }
 
 
 SamplingCircularQueue::~SamplingCircularQueue() {
+  DeleteArray(positions_);
   DeleteArray(buffer_);
 }
 
 
-void SamplingCircularQueue::SetUpProducer() {
-  producer_key_ = Thread::CreateThreadLocalKey();
-  Thread::SetThreadLocal(producer_key_, buffer_);
-}
-
-
-void SamplingCircularQueue::TearDownProducer() {
-  Thread::DeleteThreadLocalKey(producer_key_);
-}
-
-
-void SamplingCircularQueue::SetUpConsumer() {
-  consumer_key_ = Thread::CreateThreadLocalKey();
-  ConsumerPosition* cp = new ConsumerPosition;
-  cp->dequeue_chunk_pos = buffer_;
-  cp->dequeue_chunk_poll_pos = buffer_ + producer_consumer_distance_;
-  cp->dequeue_pos = NULL;
-  Thread::SetThreadLocal(consumer_key_, cp);
-}
-
-
-void SamplingCircularQueue::TearDownConsumer() {
-  delete reinterpret_cast<ConsumerPosition*>(
-      Thread::GetThreadLocal(consumer_key_));
-  Thread::DeleteThreadLocalKey(consumer_key_);
-}
-
-
 void* SamplingCircularQueue::StartDequeue() {
-  ConsumerPosition* cp = reinterpret_cast<ConsumerPosition*>(
-      Thread::GetThreadLocal(consumer_key_));
-  if (cp->dequeue_pos != NULL) {
-    return cp->dequeue_pos;
+  if (consumer_pos_->dequeue_pos != NULL) {
+    return consumer_pos_->dequeue_pos;
   } else {
-    if (*cp->dequeue_chunk_poll_pos != kClear) {
-      cp->dequeue_pos = cp->dequeue_chunk_pos;
-      cp->dequeue_end_pos = cp->dequeue_pos + chunk_size_;
-      return cp->dequeue_pos;
+    if (*consumer_pos_->dequeue_chunk_poll_pos != kClear) {
+      consumer_pos_->dequeue_pos = consumer_pos_->dequeue_chunk_pos;
+      consumer_pos_->dequeue_end_pos = consumer_pos_->dequeue_pos + chunk_size_;
+      return consumer_pos_->dequeue_pos;
     } else {
       return NULL;
     }
@@ -106,25 +98,21 @@ void* SamplingCircularQueue::StartDequeue() {
 
 
 void SamplingCircularQueue::FinishDequeue() {
-  ConsumerPosition* cp = reinterpret_cast<ConsumerPosition*>(
-      Thread::GetThreadLocal(consumer_key_));
-  cp->dequeue_pos += record_size_;
-  if (cp->dequeue_pos < cp->dequeue_end_pos) return;
+  consumer_pos_->dequeue_pos += record_size_;
+  if (consumer_pos_->dequeue_pos < consumer_pos_->dequeue_end_pos) return;
   // Move to next chunk.
-  cp->dequeue_pos = NULL;
-  *cp->dequeue_chunk_pos = kClear;
-  cp->dequeue_chunk_pos += chunk_size_;
-  WrapPositionIfNeeded(&cp->dequeue_chunk_pos);
-  cp->dequeue_chunk_poll_pos += chunk_size_;
-  WrapPositionIfNeeded(&cp->dequeue_chunk_poll_pos);
+  consumer_pos_->dequeue_pos = NULL;
+  *consumer_pos_->dequeue_chunk_pos = kClear;
+  consumer_pos_->dequeue_chunk_pos += chunk_size_;
+  WrapPositionIfNeeded(&consumer_pos_->dequeue_chunk_pos);
+  consumer_pos_->dequeue_chunk_poll_pos += chunk_size_;
+  WrapPositionIfNeeded(&consumer_pos_->dequeue_chunk_poll_pos);
 }
 
 
 void SamplingCircularQueue::FlushResidualRecords() {
-  ConsumerPosition* cp = reinterpret_cast<ConsumerPosition*>(
-      Thread::GetThreadLocal(consumer_key_));
   // Eliminate producer / consumer distance.
-  cp->dequeue_chunk_poll_pos = cp->dequeue_chunk_pos;
+  consumer_pos_->dequeue_chunk_poll_pos = consumer_pos_->dequeue_chunk_pos;
 }